I had a 13" Dell XPS at work with a 4K display. It was useless. Windows scaling is awful, and tons of programs just straight up didn't work correctly because of it. The thing had a pixel density comparable to that of my phone, which is completely and utterly pointless at normal laptop viewing distances. I ended up setting it to 1920x1080 to make it actually useful, and even then some programs were a bit wonky and I'd occasionally have to drop down to 1600x900.
A 12-13" laptop with a 4K120Hz display is just an unnecessary battery burner. Maybe once Windows scaling improves and more programs are made with high resolution assets it might make sense, but not right now.